motherboard or hard drive?

[ffxatticus]

When it locks up during boot, do you hear any beep sequences? If you do, it means that it's not getting through POST (power on self test), and that some piece of hardware is failing - quite likely to be your RAM.

It could be that your CPU or GPU is overheating when the computer freezes after being on for a while. Try downloading <a href="http://www.majorgeeks.com/download.php?det=311">Motherboard Monitor</a> and recording the temperatures when it crashes.

I think it's most likely to be your RAM or hard drive causing the problem, and as such I would immediately back up any data from your hard drive that you consider valuable. Then try downloading and booting <a href="http://www.memtest86.com/">memtest86</a>. That will tell you if it's a memory problem. Then, download <a href="http://www.hddlife.com/eng/download-freeware.html">HDDLife</a> and use that to give a rough idea of whether or not it's a drive problem. Take what it says with a grain of salt though, because it's not always right.

I don't think it's my RAM, because I replaced my RAM the other day. And it's not overheating because it happens more often right when the computer starts. I think I'm going to try backing up my HD and testing it though. Thanks for the advice.

Another possible problem is your motherboard isn't seated correctly in the computer and is touching the case, this'll make it restart alot *found that out the hard way *

This could be it, I'll take look. I remember doing a lot of chop work on the case and motherboard cuz it didn't fit when I built it.

Did you attempt to fix or upgrade the PC by yourself by any means before that problem ocurred?

Well, I built the computer and it's been happening since then pretty much.